You might find the suspension culture described by Steve Gleddie of
Agriculture Canada suitable for your purposes.
Steve is probably not connected up to this BB yet, but you can contact
him at: The Plant Research Centre Agriculture canada Ottawa Ontario
CANADA K1A 0C6 (613) 995 3700
The relevant paper for this suspension is: Plant Cell Reports 8 1-5
(1989)
Hope this will be of help.
Maurice Moloney University of Calgary